Drum mixer for continuous processing of a granular bulk material

ABSTRACT

For preparing a granular bulk material for use, such as in reclaiming foundry sand, a drum mixer is arranged to rotate about a shaft located at an acute angle to the horizontal. The circumferential side of the drum is closed while one transverse end is closed and the other is open. The shaft rotates the drum at a speed so that a portion of the bulk material, as it moves with the drum, drops in a free fall through the drum. A mixing and kneading tool extends into the bulk material in the drum, preferably into the center of gravity of the bulk material, and the drum, and the tool is rotated so that it provides a flow within the bulk material countercurrent to the flow generated by the rotation of the drum. Further, a pair of the mixing and kneading tools can be used, each rotating opposite to the other.

United States Patent 1 1 Tegelhutter 1 Oct. 1, 1974 [54] DRUM MIXER FORCONTINUOUS 3,674,241 7/1972 Eirich et al. 259 15 PRQCESSING ()F AGRANULAR BULK 3,690,622 9/1972 Brunner 259/174 X MATERIAL Inventor:Herbert Tegelhutter, Velbert,

Germany Assignee: Georg Fischer Aktiengesellschaft,

Schaffhausen, Switzerland Filed: Jan. 19, 1972 Appl. No: 218,937

Foreign Application Priority Data Jan. 21, 1971 Switzerland 874/71References Cited UNITED STATES PATENTS 13uhrer,...,,.. 259/3 Katzer eta1 259/1 Primary ExaminerHarvey C. I-Iornsby Assistant Examiner-AlanCantor Attorney, Agent, or FirmToren and McGeady 5 7 ABSTRACT Forpreparing a granular bulk material for use, such as in reclaimingfoundry sand, a drum mixer is arranged to rotate about a shaft locatedat an acute angle to the horizontal. The circumferential side of thedrum is closed while one transverse end is closed and the other is open.The shaft rotates the drum at a speed so that a portion of the bulkmaterial, as it moves with the drum, drops in a free fall through thedrum. A mixing and kneading tool extends into the bulk material in thedrum, preferably into the center of gravity of the bulk material, andthe drum, and the tool is rotated so that it provides a flow within thebulk mate rial countercurrent to the flow generated by the rotation ofthe drum. Further, a pair of the mixing and kneading tools can be used,each rotating opposite to the other.

' 4 Claims, 4 Drawing Figures DRUM MIXER FOR CONTINUOUS PROCESSING OF AGRANULAR BULK MATERIAL SUMMARY OF THE INVENTION The present invention isdirected to a drum mixer for the continuous processing of granular bulkmaterial, especially for reclaiming foundry sand, and, moreparticularly, it concerns the arrangement of the drum mixer which isadapted to rotate about an axis inclined to the horizontal with the drumrotating at such a speed that a portion of the material charged into thedrum drops in a free fall as the material is moved by the rotation ofthe drum.

As is well known, when sand molds are cast the foundry sanddirectly'adjacent the cast piece is heated to a considerable extentwhile the foundry sand more remote from the cast piece remains at a lowtemperature. Accordingly, when a mold is emptied, some of the foundrysand is very moist and at a relatively low temperature, while anotherportion is relatively hot and completely dry. The very moist orover-humidified sand tends to form lumps of various sizes when it ismixed with the dried-out sand. However, it is important, for thereprocessing and reuse of the foundry sand that it be in a relativelylump-free condition and of uniform moisture and temperature.

In reclaiming foundry sand an apparatus has been used which includes adrum arranged to rotate about an axis inclined to the horizontal, withthe drum closed on the side and at one end and open on the other. Thedimension between the opened and closed ends of the drum is less thanits diameter. Further, driving means are provided for the drum so thatit rotates at a speed which permits a portion of the foundry sand withinthe drum to drop in a free fall. It has been found that the eliminationof the lumps in the foundry sand at times presents difficulties for thisapparatus.

There is another known apparatus which uses a mixing tool extending intothe foundry sand for mixing the sand and at the same time moistening it.However, in such an arrangement the aeration and cooling of the sandleaves much to be desired.

For use in forming molds, reclaimed foundry sand must have certainmechanical properties, for example, strength, permeability and the like,and, in addition, it must be lumpfree, aerated and homogeneouslymoistened, accordingly, it is the primary object of the presentinvention to provide an arrangement which meets the foregoingrequirements for reclaimed foundry sand. Commencing with the known typeof drum mixer indicated above, the present invention incorporates atleast one rotating mixing and kneading tool of a mixing apparatus whichis preferably positioned in the center of gravity of the compact bulkmaterial located within the lower region of the drum. The characterizingfeature of the use of the mixing and kneading tool is that it is rotatedwithin the material so that it provides a flow within the materialcounter current to the flow developed by the drum as it rotates.

Therefore, in accordance with the present invention, it is possible toadequately reprocess the foundry sand so that it is mixed, kneaded andloosened at a considerable reduction in equipment costs and a betterquality of reclaimed foundry sand can be obtained.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure.

For a better understanding of the invention, its operating advantagesand specific objects attained by its use, reference should be had to theaccompanying drawings and descriptive matter in which there areillustrated and described preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a vertical sectional view through a mixing apparatus embodyingthe present invention;

FIG. 2 is a schematic representation of the manner in which the materialis moved within the mixing appara tus;

FIG. 3 is a schematic representation of the flow of the material withinthe mixing apparatus due to the combined action of a drum and a mixingand kneading tool; and

FIG. 4 is a schematic representation, similar to that in FIG. 3, inwhich a pair of mixing and kneading tools are positioned within thematerial.

DETAILED DESCRIPTION OF THE INVENTION In FIG. 1 a mixing apparatus forreprocessing foundry sand is illustrated and includes a drum mixer Imounted on a centrally arranged drum shaft 2 for rotation about an axisarranged at an acute angle to the horizontal. The drum mixer l is formedby a conically shaped drum bottom or end 15 to which the shaft 2 isattached with a circumferentially extending wall extending axially fromthe end 15. Opposite the end 15 the drum is open and an edge member orflange 14 extends inwardly from the side of the drum and the inwardlyextending dimension of the flange l4 determines the height of thecompact foundry sand 7 within the lower portion of the drum 1, noteFIG. 1. The drum shaft 2 is connected to a drive 3' and it is rotatablymounted in a pair of axially spaced bearings 4,4. To provide acontinuous supply of the foundry sand into the drum, a conveyor belt 8is located above the open end of the drum. Another conveyor belt 9 islocated below the drum for the continuous discharge of the reclaimedfoundry sand which flows over the flange 14 on the drum.

Extending into the foundry sand through the open end of the drum is amixing and kneading tool 5 driven by a known mixing apparatus 6.Preferably, the tool 5 extends into the center of gravity of the foundrysand 7 in the lower portion of the drum. The mixing apparatus 6 ismovably mounted for maintaining the tool 5 at the center of gravity ofthe foundry sand 7 and it includes a follow-up device for the automaticguidance of the mixing and kneading tool.

A pipe line 12 having a nozzle 13 at its end extends into the druml sothat the nozzle is located above the body of the foundry sand 7 andserves to direct a supply of water into the sand. Within the pipe line12 a valve 16 is arranged in communication with a control line 11 whichextends to a control device 10. As can be noted in FIG. 1, measuringlines 26 extend between the control device 10 and the driving motor 6 ofthe mixing and kneading tool 5 so that the addition of water can beregulated in dependence on the input of the driving motor 6.

Clay-binders, coal dust and other substances can be added to the foundrysand either separately or with the water through the nozzle 13 byproviding a proper design for the nozzle. In one embodiment, additionalsubstances in the form of a slurry can be introduced into the pipe line12 through a branch pipe 24 which is connected to a dosing device 25. Asindicated above, it is also possible to supply these substances into thedrum without using the pipe line 12 and the nozzle 13.

In FIG. 2 a schematic representation is provided of the manner in whichthe granular bulk material or foundry sand travels within the drum asthe drum rotates. The speed of the drum 1 and of the variably insertablemixing and kneading tool 5, as well as the inclination of the shaft 2for the drum, depend to a great extent on the type and composition ofthe foundry sand being reprocessed. With a properly selected ratio ofspeed and inclination of the shaft 2 and of the mixing and kneading tool5, the foundry sand within the drum can be divided. As a rule, the speedof the drum 1 will be slower than that of the mixing and kneading tool5.

As the drum rotates in the direction of the arrow shown in FIG. 2, aportion 17 of the foundry sand charged into the drum after exceeding theangle of repose of the sand slides back downwardly in an avalanche-likemanner across the top of the body of foundry sand 7. This avalanche-likeflow takes place without any detachment or separation of the foundrysand from the remaining compact body 7 of the sand. Another portion 19of the foundry sand returns into the starting position passing along theclosed end 15 of the drum and mixes with the compact body 7 at the point18 on the drum within its lower region. In FIG. 2 a portion of theflange 14 is shown removed to indicate the various paths of flow of thefoundry sand due to the action of the drum rotation.

Yet a third portion 20 of the sand is carried upwardly above the angleof repose and detaches itself from the drum 1 and returns in a free fallas a spray of sand through the portions 17 and 19. Further, the mixingand kneading tool 5 contributes to the circulation of the compact body 7of the sand and the direction of rotation of the tool is opposite to thedirection of rotation of the drum. The oppositely directed rotation ofthe tool provides a counter-current flow 21 in the sand relative to theflow provided by the drum. Due to the counter-current flow 21, themixing and separation of the sand is intensified, because the individualgrains of sand rub each other and are thus refined. Moreover, due to thewhirling movement of the mixing and kneading tool 5, air is introducedinto the foundry sand with the result that a particularly loose andmoldable sand is obtained.

FIG. 3 is a schematic showing of the bii'atififiii? mixing and kneadingtool 5 in a cross section of the body 7 of the foundry sand, showing thecountercurrent flow 21 to the flow of the sand developed by the drum.

In FIG. 4 a schematic representation is provided of the manner in whichtwo spaced mixing and kneading tools 5', 5", which rotate in oppositedirections, provide an intensified mixing action within the compact body7 of the foundry sand.

M What is claimed is:

1. Drum mixer for th e contiiiuous pTo cessing of 5' tending radiallyinwardly from the end of said closed side spaced outwardly from saidclosed end and the radially inner edge of said flange defining theopening in the opened end of said drum, means for supplying granularbulk material into said drum so that a compact body of material isformed in the lower portion of said drum with the surface of the body ofmaterial sloping downwardly from said closed end to said radially inneredge of said flange in the lower portion of said drum and with the saidradially inner edge forming an outlet edge over which the processedmaterial flows from said drum, said first driving means arranged torotate said drum at a speed so that the compact body of material remainsin the lower portion of said drum, wherein the improvement comprises amixing and kneading tool mounting such that it extends into said drumbelow the axis of rotation of said drum and said tool having a head endarranged to be positioned below the downwardly sloping surface of thecompact body of material within the lower part of said drum such that itis located at the center of gravity of the body of material for mixingand kneading said material, second drive means operably connected tosaid tool for rotating said tool in a direction counter-current to thedirection of rotation of said drum so that said tool provides a flow inthe body of material counter-current to the direction of flow of thematerial developed by said drum, and said second driving means and saidtool being movably mounted for maintaining the head end of said tool atthe center of gravity of the material.

2. Drum mixer, as set forth in claim 1,'wherein a pipe line having anozzle at its end is arranged for spraying water into the body ofmaterial in the lower portion of said drum with said nozzle spaced abovethe body of material, a branch pipe connected to said pipe line foradding solid substances in powder, granular and slurry form into saidpipe line for introduction into the material in said drum through saidnozzle.

3. Drum mixer, as set forth in claim 2, wherein a valve is positioned insaid pipe line, a control device connected to said second driving means,a control line extending between said control device and said valve, sothat the addition of water into said drum through said pipe line can beregulated in dependence on the imput of said second driving means.

4. Drum mixer, as set forth in claim 1, wherein at least two mixing andkneading tools are arranged within the compact body of the within saiddrum.

granular material.

1. Drum mixer for the continuous processing of a granular bulk material,such as foundry sand, including a rotatable shaft disposed at an acuteangle to the horizontal, first driving means operatively connected tosaid shaft, a drum mounted on said shaft for rotation therewith, saiddrum comprising a closed end secured to and extending transversely ofsaid shaft, an annular shaped closed side secured at one end to saidclosed end and extending outwardly therefrom in the axial direction ofsaid shaft with said closed side sloping upwardly from said closed end,and an annular flange extending radially inwardly from the end of saidclosed side spaced outwardly from said closed end and the radially inneredge of said flange defining the opening in the opened end of said drum,means for supplying granular bulk material into said drum so that acompact body of material is formed in the lower portion of said drumwiTh the surface of the body of material sloping downwardly from saidclosed end to said radially inner edge of said flange in the lowerportion of said drum and with the said radially inner edge forming anoutlet edge over which the processed material flows from said drum, saidfirst driving means arranged to rotate said drum at a speed so that thecompact body of material remains in the lower portion of said drum,wherein the improvement comprises a mixing and kneading tool mountingsuch that it extends into said drum below the axis of rotation of saiddrum and said tool having a head end arranged to be positioned below thedownwardly sloping surface of the compact body of material within thelower part of said drum such that it is located at the center of gravityof the body of material for mixing and kneading said material, seconddrive means operably connected to said tool for rotating said tool in adirection counter-current to the direction of rotation of said drum sothat said tool provides a flow in the body of material counter-currentto the direction of flow of the material developed by said drum, andsaid second driving means and said tool being movably mounted formaintaining the head end of said tool at the center of gravity of thematerial.
 2. Drum mixer, as set forth in claim 1, wherein a pipe linehaving a nozzle at its end is arranged for spraying water into the bodyof material in the lower portion of said drum with said nozzle spacedabove the body of material, a branch pipe connected to said pipe linefor adding solid substances in powder, granular and slurry form intosaid pipe line for introduction into the material in said drum throughsaid nozzle.
 3. Drum mixer, as set forth in claim 2, wherein a valve ispositioned in said pipe line, a control device connected to said seconddriving means, a control line extending between said control device andsaid valve, so that the addition of water into said drum through saidpipe line can be regulated in dependence on the imput of said seconddriving means.
 4. Drum mixer, as set forth in claim 1, wherein at leasttwo mixing and kneading tools are arranged within the compact body ofthe granular material within said drum.